Electric-arc furnace.



I. RENNERFELT.

Patented Feb. 18, 1919.

2 SHEETS-SHEET 2.

[n venfor' PATENT OFFICE;

IVAR Runner-tram, on DJ'UBSHQLM, swnnnn.

ELECTRIC-ARC FUItNACE.

Specification or Letters Patent.

' Application filed Au ust 24, 1916. Serial No. 116,837.

To all whom it may concern:

Be it known that 1, Ivan RENNERFELT, a subject of the Kiiig of Sweden, residing at Djursholm, in the ingdom of Sweden, have 6 invented a new and useful Improvement in' Electric-Arc Furnaces, ofwhlich the followingz isa specification.

lectric arc furnaces. are previously known which are provided with a heating chamber 10 for receiving the material to be heated and with an electric arc chamber separated from the said heating chamber, in which electric arc chamber the electric arcs serving for heating the material are generated. In furnaces of this kind the heat will of course be better utilized if the generated arcs are made to contact with the wall between the electric arc chamber and the heating chamber, that is to say, with the wall ofthe retort in case the heating chamber consists. of a retort placed in the electric arc chamber. It has already been proposed'to have the retort form one of the electrodes and to generate the arc or arcs between the retort" and one or more other electrodes in the electric arc chamber. Such furnaces are encumbered with the disadvantage, however, that when starting the furname, when the electrodes must be moved into I contact with the retort or the wall and, acu cordingly, the resistance becomes com arativelysmall, a'stron rush of current w1ll be formed, and for this reason such furnaces, are not well adapted for use on circuits with, constant tension, such as a lighting circuit, without the use of damping coils, starting resistances, ,or the like. f The primary object of the present inven- =tion is to. avoid this disadvantage and tomakethe furnace capable of being used directly on, for instance, lighting circuits without the use of any special starting devices. For this purpose the invention is broadly characterized by this that the. electric arc chamber and the chamber or chambers in which the material is" heated, areseparated by means of a preferably refractory and pulverized resistance material and that the electrodes are arranged in such manner in the electric arc chamber that the electric arcs formed by the electrodes are closed by the The said resist 50 said resistance material.

" ance material consists preferably of finely PatentedFeb. 18-, 1919.

pulverized graphite or coke and it isso U mensioned that the principal generation of heat is effected by the arcs. When the furnace is started in cold state, however, the said resistance 'm-aterial'servesas a starting; resistance which prevents the generation of' strong rushes of current, thus making it unnecessary to use any special apparatus for the starting. As the resistance of the mate,-

rial is decreased when heated the electrodes are withdrawn, thus insuring a smooth and the present invention renders possiblethe use easy starting of the furnace- Accordingly,

of electric current as a source of heat also in q such cases wherev the amount of energy a-vailable is comparatively small, and'the conditions do notallow, even temporarily, the consumption of current to exceed certain limits.v

By the use of the resistance material the heat will also be more uniformly distributedin the heating chamber.

In order to render possible a continuous heating without the furnace having. tohe wholly or partly taken to pieces at intervals, 1

apertures are provided in the walls or in the-1 bottom of the furnace hearth, through which apertures the material to be heated may be introduced in the furnace. Graphitization of carbon electrodes may thus. be performed in such manner that they are introduced at one side o'f the furnace and removed at the otherside thereofafter having been heated by-the heat fromthe electric arcs during a sufiiciently long time. If the electrodes. are

slowly moved through said apertures, they may be preheated and cooled simultaneously in the bottom or walls ofthe hearth without. appreciable oxidation,:. provided that" the bottom and walls are made sufficiently thick for the purpose. Below the electricarcs a suitable'quantity of preferably pulverized carbon or graphite is placed'as contact mate-- rial. Fresh carbon or graphitepowderis' preferably introducedthrough apertures in 'the vault of the furnace or through the'openings for the electrodes. In orderthat the powder shall notprevent the feeding for-,

ward of the electrodes to be treated, it'is suitable to provide channels covered by slabs,

in the bottom of the furnace, in which shap nels the electrodeshre fed forward during the process of graphitizat ont Accord ng to tures to retorts having higher 'neath the arcs a barge of 'simultaneo a modification of the invention the bottom of the furnace may also be movable in a horizontal-or vertical direction for the purpose of making it possible to introduce be many electrodes sly.

Accor'dingto the invention the furnace may also be constructed in such manner that the heating chamber, for instance a retort or a cupel-furnace, isbompletely embedded in By also embedding .a contact in the material and by supplying current to this contact heat may also be generated in the resistance material in addition ,to the heat generated by the arcs.

of heat from the .arc zone to the interior of the, retort 'isobtained owing to the high thermal conductivity of the material used. A further advantage is that the retort will not be (lama ed or melted by superheating" the same? he .retort may, of course, also be made from other refractory materials,

such as carborundiun, magnesite, lire-clay, and so forth. It may be constructed round, square, or any other shape desired. A number of retorts embedded one over the other or side by side, may also be used, if desired, whereby the material ma be transferred gradually from retorts 0 lower temperatemperatures. If desired, the retort may be provided with means for circulation of gases.

In the accompanying drawings a few embodiments of furnaces suitable for perfornv ing the present process, way of example. Figure 1 shows a vertical longitudinal section of a furnace provided with three electrodes, in the bottom of which furnace there are channels for receiving the carbon electrodes or other material to be heated. Fig. 2 shows a vertical cross sec tion of the same furnace on the line lib-ll in Fig. 1. I Fig. 3 shows a vertical cross section of a furnace as shown in. Fig. 1 but provided with a cylindrical bottom in which there is a number of channels. Fig; 3 may also be regarded as a horizontal cross section of a furnace having a vertical shaft or chamber. Fig. l shows a verticalcross section, and Fig. 5 a vertical longitudinal section of a third embodiment, of which Fig. 6" shows a detail. v

Referring to Figs. 1 and 2, the furnace is shown provided with-vertical electrodes 1 projecting into the same through apertures in the vault 2 and insulated from the same. These electrodes generate arcs 3 contacting with carbon powder l on jthe bottom 5. The bottom and the walls of the hearth are made from. a very refractory material, preferably carbon'briclr. in the bottom there are long channels 6 into which the charge 7 may be in which time it may The retort may be made from graphite trodes through or carbon, whereby an increased conductlon the bottom have been shown by.

arcs formed by the electrodes are are chamber, a preferably refractory essence troduced at one side of the furnace, and be removed at the other side thereof at be simultaneously preheated and cooled. lhe interior carbon lining of the furnace is surrounded by magnesite brick or the like and is well insulated 7o by means of asbestos or other suitable material to prevent heat loss. The walls oi" the furnace are suitably provided with. apertures S for introducing carbon powder, when required, and for examining the in- 7s terior of the furnace. "The" apertures 9 through which the electrodes 1 project into .the'furnace, are of comparatively large size in order to prevent discharges from the elec-- the conducting brickwork so in the furnace shown in Fig. 3 the bottom a of the'hearth is of cylindrical shape andin.

and the walls ther is provideda plurality of channels it.

The furnace illustrated in Figs. 4A) is pro- 35 vided withan ole-c rode or are chamber 1-1 and an electrode 12 projecting into the same. The electrode generates an are 13 contacting with a more or less finely divided conductor ll. Below the are a chamber i5 is arso ranged in the conductor let, this chamber being .rormed, in the instance shown, by means of a retort or a cupel furnace 16. Be low this cu pel-lurnace it there is a conductive mass or body 1'? in'which therois an as electrode 18 or other contact for the current forming the are 13. The walls 19 of the electrode chamber ll and of the chamber 15 are made from a very refractory material, such as magnesite, carborundum, or the like. For feeding the electrode 12 downward there is arranged on the furnace a screw 2'1 and hand-wheel 20 which actuates an arm 299 connected at 23 in any suitable manner to the electrode 12.

- I claim:

1. In an electric arc furnace, the combina. tion of an. electric arc chamber, a heating chamber for receiving the material to behea'ted, a partition consisting of a ably refractory and pulverized resistance material between said chambers, and electrodes projecting into said electric arc chamber in such manner that the electric closed by the said refractory resistance material,

2. In an electric arc furnace, the combination-of an electric arc chamber,a heating chamber for receiving the material to be. heated formed in the bottom of saidelectric and pulverized resistance material covering the bottom of said electric arc chamber, and electrodes projecting into said. electric arc chamberin such manner that the electric arcs formed by the electrodes are closed by the said refractory resistance material.

3. in an electric furnace, the corrbi carbon brick, chamotte, oo

prefer no 5 heating chamber said electric are chamberin such manner that the electric arcs formed by the electrodes are closed by the said refractory resistance material; and an electric contaetembedded in said resistance material.

IVAR RENNERFEL' 

